This invention relates to suspension systems for automotive vehicles and more particularly to a stabilizer bar for a suspension system.
The typical passenger automobile has independently suspended front wheels, as do similar vehicles, such as sports utility vehicles, vans, and light trucks. In order to prevent excessive body roll in such vehicles when they negotiate turns, particularly at higher speeds, the vehicles are equipped with stabilizer bars that connect the sides of their front suspensions. Each side on such a vehicle includes at least one control arm and a steering knuckle to which a wheel end is attached, with one of the front wheels being mounted on the wheel end. The stabilizer bar constitutes nothing more than a torsion bar that extends transversely across the front of the vehicle where it is attached to the frame or body of the vehicle, yet is free to rotate. At its ends, the stabilizer bar has torque arms which are attached to the control arms. As a consequence, the control arms tend to move in unison in the same direction and transfer forces to the frame—forces which modulate and retard roll.
While a stabilizer bar will improve the control and orientation of a vehicle when the vehicle negotiates a turn, particularly at high speeds on paved surfaces, it detracts from the ride when the vehicle travels along straight road surfaces. Moreover, it makes travel at low speeds, either straight or through turns, more uncomfortable than it could otherwise be. After all, when one wheel is deflected upwardly, such as by encountering a bump, the other wheel will attempt to lift as well, since the stabilizer bar connects the control arms for both wheels, and oppositely directed forces are applied to the vehicle frame. This can produce a rocking motion when the vehicle travels off road or over uneven road surfaces—a phenomenon sometimes referred to as “antiroll bar waddle”. Hence, different driving conditions call for stabilizer bars with different torsional stiffness. At one extreme are the conditions encountered off road and on secondary roads traveled at relatively low speeds and also those encountered on straight segments of paved roads. These conditions require low torsional stiffness. At the other extreme are the conditions encountered when negotiating turns on paved surfaces at high speeds. These conditions require high stiffness. Most stabilizer bars have high stiffness to resist roll and maintain control in turns.